Sorry for your loss.
As for wether you could have done something...I think it's particularly difficult with family.
I lost an uncle 3/4 years ago who had struggled for years. I think his death was pretty gruesome and directly linked to a drinking binge. His daughter asked me several times to speak to him.
I'd met with him a few times anyway, the fact I wasn't drinking anymore came up and he was curious. Spoke as if he'd already done his own 'research' and come to his own conclusions so to speak. I even had a copy of the AA big book on me once (by coincidence), he saw it in my bag and asked.
At the end of the day I did the only thing I could...be sober and be available as someone to talk to. That wasn't enough because the other 50% had to come from him.
Take care congrats on your sobriety
P